A lattice fluid model, Sanchez-Lacombe equation, is used to predict the phase behavior for a styrene/CO2/polystyrene ternary sys-tem. The binary parameters involved in the equation were optimized using experimental da...A lattice fluid model, Sanchez-Lacombe equation, is used to predict the phase behavior for a styrene/CO2/polystyrene ternary sys-tem. The binary parameters involved in the equation were optimized using experimental data. Phase diagrams and the distribution coefficients of styrene between polymer phase and fluid phase are obtained over a wide range of pressure, temperature and composition. The analysis of ter-nary phase diagrams indicates that this system at relatively high pressure or low temperature may display two-phase equilibrium, and at low pressures or high temperatures three-phase equilibrium may appear. The distribution coefficients of styrene between the fluid phase and the polymer phase increase asymptotically to unity when the concentration of styrene increases. The results provide thermodynamic knowledge for further exploitation of supercritical carbon dioxide assisted devolatilization and impregnation.展开更多
In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical noz...In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.展开更多
A simulation for piston effect in supercritical carbon dioxide by employing a simple model is conducted. In the first place, the thermal properties of carbon dioxide near its liquid-vapor critical point are discussed....A simulation for piston effect in supercritical carbon dioxide by employing a simple model is conducted. In the first place, the thermal properties of carbon dioxide near its liquid-vapor critical point are discussed. It is calcu- lated that the heat capacity ratio and isobaric expansion coefficient of supercritical fluids are extremely high. Furthermore, the simulation for piston effect in supereritical carbon dioxide between two infinite vertical walls is presented. The numerical results prove that piston effect has a much faster speed of heat transfer than thermal conduction under mierogravity conditions. Moreover, the piston effect turns out to be stronger when closer to the critical point.展开更多
The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon di...The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon dioxide refrigeration system.However,the supercritical fluid leakage in expander is serious and is the main factor affecting the expander's efficiency.This paper presented and compared four classic leakage models.The analysis indicated that laminar leakage model is suitable in leakage simulation of expander.A leakage test system,including the leakage test part which has two types of leakage specimens with different gaps ranging from 5 to 15 m,was established.The experimental results indicated that lubricant film played an important role.When the leakage clearance of cylindrical specimen was 5 m,the mass flow rate of leakage was about 0.88 g s-1.The data was 3.638 g s-1 with leakage clearance being 10 m and 7.11g s-1 with leakage clearance being 15 m.A modified leakage model was developed,whose average deviation was within 10% compared with the experimental data.At last,this paper simulated the leakage in rolling piston expander presented by Tian et al.(2010).The leakage between rolling piston and cylinder was the most serious part with the value up to 0.04 kg s-1.展开更多
基金Supported by the National Natural Science Foundation of China (No. 29676037).
文摘A lattice fluid model, Sanchez-Lacombe equation, is used to predict the phase behavior for a styrene/CO2/polystyrene ternary sys-tem. The binary parameters involved in the equation were optimized using experimental data. Phase diagrams and the distribution coefficients of styrene between polymer phase and fluid phase are obtained over a wide range of pressure, temperature and composition. The analysis of ter-nary phase diagrams indicates that this system at relatively high pressure or low temperature may display two-phase equilibrium, and at low pressures or high temperatures three-phase equilibrium may appear. The distribution coefficients of styrene between the fluid phase and the polymer phase increase asymptotically to unity when the concentration of styrene increases. The results provide thermodynamic knowledge for further exploitation of supercritical carbon dioxide assisted devolatilization and impregnation.
文摘In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.
基金financially supported by the National Basic Research Program of China (973 Program) under Grant No.2012CB933200the National Natural Science Foundation of China under Grant No.51161140332
文摘A simulation for piston effect in supercritical carbon dioxide by employing a simple model is conducted. In the first place, the thermal properties of carbon dioxide near its liquid-vapor critical point are discussed. It is calcu- lated that the heat capacity ratio and isobaric expansion coefficient of supercritical fluids are extremely high. Furthermore, the simulation for piston effect in supereritical carbon dioxide between two infinite vertical walls is presented. The numerical results prove that piston effect has a much faster speed of heat transfer than thermal conduction under mierogravity conditions. Moreover, the piston effect turns out to be stronger when closer to the critical point.
基金supported by the National Natural Science Foundation of China (Grant No. 50676064)
文摘The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon dioxide refrigeration system.However,the supercritical fluid leakage in expander is serious and is the main factor affecting the expander's efficiency.This paper presented and compared four classic leakage models.The analysis indicated that laminar leakage model is suitable in leakage simulation of expander.A leakage test system,including the leakage test part which has two types of leakage specimens with different gaps ranging from 5 to 15 m,was established.The experimental results indicated that lubricant film played an important role.When the leakage clearance of cylindrical specimen was 5 m,the mass flow rate of leakage was about 0.88 g s-1.The data was 3.638 g s-1 with leakage clearance being 10 m and 7.11g s-1 with leakage clearance being 15 m.A modified leakage model was developed,whose average deviation was within 10% compared with the experimental data.At last,this paper simulated the leakage in rolling piston expander presented by Tian et al.(2010).The leakage between rolling piston and cylinder was the most serious part with the value up to 0.04 kg s-1.
